Light production

Thanks to Rebekah Wilkins, Jackie O’Riley

Perciformes

LophiiformesPerciformes

Light production in fishes

Who?scattered among 13 orders, 45 families (Bond Table 19-1)

mostly in teleosts, 2 families of elasmobranches

Where? mostly deep sea, 300-1,000mup to 2/3 of deep oceanic fishes produce light600-700 species of mesopelagic fishes

How?

General principle: production of light by ‘cold’ chemical reaction:

luciferase

Luciferin + O2 + ATP oxyluciferin + light

How?

1. produce luciferin – usually under neural controlmay have lens or iris to control emission of light

2. rob luciferin from dietconcentrate it in specialized areas of body

3. contain symbiotic bacteria in special structuresprobably derived from dietocclude with tissue or pigment to ‘flash’ light

Why?

1. Predation – reduces prey-seeking energy and timelures on anglerfisheson inside of mouth (Sternoptyx, Psueodscopelus)mimic lures of dragonfishes may mimic prey conspecificscookie cutter shark may appear smaller, less threatening

Anglerfish Dragonfish Sternoptyx

Why?

1. Predation – reduces prey-seeking energy and timelures on anglerfisheson inside of mouth (Sternoptyx, Psueodscopelus)mimic lures of dragonfishes may mimic prey conspecificscookie cutter shark may appear smaller, less threatening

Anglerfish Dragonfish Sternoptyx Lophiiformes Lophiiformes Stomiiformes

Why?

1. Predation – reduces prey-seeking energy and timelures on anglerfisheson inside of mouth (Sternoptyx, Psueodscopelus)mimic lures of dragonfishes may mimic prey conspecificscookie cutter shark may appear smaller, less threatening

2. Predation – see prey better‘flashlights’ under eyes, or in mouthred light of black dragonfish, not visible to prey

Why?

3. Defensecountershading on ventral surface (hatchefishes)

Stomiiformes

Counter illumination

Why?

3. Defensecountershading on ventral surface (hatchefishes)intimidation – appear larger (elongate dragonfish)confuse or startle predator – flashlight fish apparently change

position with each flash

Beryciformes

Why?

3. Defensecountershading on ventral surface (hatchefishes)intimidation – appear larger (elongate dragonfish)confuse or startle predator – flashlight fish apparently change

position with each flash

4. Communicationaggregate conspecifics (flashlight fish)

Why?

5. Sexual selection?Melanostomias male is brighter – female may select by brightness

Control:

lens or iris-like structures control light emission tissue or pigment occlusion allows ‘flashing’ cover the photophore with a membrane or rotate it inward

Shining Tubeshoulder

•Photophores on underside

•Tube on each shoulder

• Squirts bioluminescent ink at predators